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Photon-photon collisions and photon "decay"

  1. Feb 15, 2015 #1
    Hello.

    I want to play around with the process of one photon splitting into more lower energy photons and vice versa.

    As I understand it one can quite easily make a Feynman diagram of a photon splitting into two lower energy photons by interacting with virtual electron/positrons. And also the reverse diagram is possible.

    Questions:
    - Once after getting the Feynman amplitudes for the splitting process, can one use the golden rule for Decays in a straight forward manner as one could for weak decays?

    - Which diagrams are more dominant? Is it sufficient to just use gamma -> gamma gamma, or is it necessary to for instance also include gamma -> gamma gamma gamma.
     
  2. jcsd
  3. Feb 15, 2015 #2

    mfb

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    Yes, but it won't happen in vacuum, all the amplitudes add to zero.
    I don't find the reference I was looking for, but here one that needs to introduce violations of Lorentz invariance for the process: arXiv:hep-ph/0212382
     
  4. Feb 15, 2015 #3
    Okay, thanks =)
    Are there any other similar processes that allow for this kind of phenomenon(photons splitting or merging). I saw a paper on gamma -> 3xgamma, but that was in a strong magnetic field. How about 2xgamma -> 3xgamma ?
     
  5. Feb 15, 2015 #4

    mfb

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    That might work (but odd<->even tends to be tricky as far as I know).
    2 photons -> 2 photons or 4 photons certainly works, but the cross-section is really tiny.
     
  6. Feb 15, 2015 #5

    Vanadium 50

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    Odd -> even (and vice versa) will never work. (proven by Wendell Furry)

    Momentum-energy conservation strongly constrains what processes are allowed.
     
  7. Feb 15, 2015 #6

    PAllen

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  8. Feb 16, 2015 #7

    jimgraber

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    Last edited: Feb 16, 2015
  9. Feb 16, 2015 #8

    jimgraber

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    One quote from the reference in my previous post:
    "The whole process appears as two photons ricocheting off each other, but it has only been observed indirectly by its effect on the magnetic moments of the electron and muon."
     
  10. Feb 16, 2015 #9

    mfb

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    I didn't see this analysis, but to separate 20 events per year from background you need an extremely clean signature. Like particles in the TeV-range, and I would be surprised if they expect their production.
     
  11. Feb 16, 2015 #10

    bcrowell

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  12. Feb 17, 2015 #11

    vanhees71

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    As far as I know, Delbrück scattering has not been observed yet, but there's nothing in principle against it. To the contrary, since it's a QED process, I'd expect it to really exist and even the prediction of the cross section should be quantitatively correct.
     
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